Radiator Fan Wiring 88 DL

[subaru1988]

Hi All,

So I'm trying to verify what should be a real simple wiring hookup for my '88 DL with no air cond.- the radiator fan, and the thermoswitch. Long story short, my Rad fan connector got hot and melted due to corrosion, and I had to redo all the ends with spade connectors. This obviously meant I had to cut the other wires and redo them with spades too. I was dumb enough to not label the wires 🤨.

I'm going by this diagram- the wiring colors seem to be the same except for the thermoswitch, which for some reason shows a black and yellow wire where I have two black wires. I have my stuff connected:

Blue/Red from Harness to Blue/Red on Fan
Black Thermoswitch to Black Harness
Black Thermoswitch to Yellow/White Harness
Yellow/White Fan to Yellow/White Harness

The diagram shows the male connectors, but not the female off the harness, which leaves me wondering if I mixed up one or two. My car runs midpoint and slightly under on the gauge, and I don't hear the fan coming on. I know the fan works. I jumpered it to verify a short time BEFORE the wire connector changes. Not sure which of the connectors I'd do that with anymore! Any input to verify my wiring would be much appreciated!

 

Edited April 7 by subaru1988
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[azdave]

The only thing critical is that the blue/red wire on the fan sees positive voltage and that the yellow/white gets a ground that comes from the thermo snap switch. The wires on the thermo snap switch could get swapped but is doesn't matter since all it is doing is supplying the ground connection for the fan whenever the coolant is hot enough.

When the key is on and the engine either hot or cold, you should always read +12 volts on one wire going to the snap switch connector. The other wire will be grounded to the chassis. When the coolant is hot enough, the snap switch closes and the fan is connected to ground and turns on. You could have the wires on the snap switch reversed and it would not matter. To test the fan, temporarily jumper across the connector at the snap switch with a paper clip (ignition key in the run position) and the fan should turn on. That tells you if the fan is okay. To test the snap switch, you will need to get it hot enough to trigger it. If you can take it out easily, connect it to a VOM and heat it in a pan of boiling water to see if the contacts go from open to closed.

Edited April 8 by azdave

[subaru1988]

On 4/8/2025 at 2:26 PM, azdave said:

The only thing critical is that the blue/red wire on the fan sees positive voltage and that the yellow/white gets a ground that comes from the thermo snap switch. The wires on the thermo snap switch could get swapped but is doesn't matter since all it is doing is supplying the ground connection for the fan whenever the coolant is hot enough.

When the key is on and the engine either hot or cold, you should always read +12 volts on one wire going to the snap switch connector. The other wire will be grounded to the chassis. When the coolant is hot enough, the snap switch closes and the fan is connected to ground and turns on. You could have the wires on the snap switch reversed and it would not matter. To test the fan, temporarily jumper across the connector at the snap switch with a paper clip (ignition key in the run position) and the fan should turn on. That tells you if the fan is okay. To test the snap switch, you will need to get it hot enough to trigger it. If you can take it out easily, connect it to a VOM and heat it in a pan of boiling water to see if the contacts go from open to closed.

Thanks for the input, I appreciate it. You cleared a few things up for me. First, I know for sure the blue/red to blue/red is right. Second, the reason the wires on the aftermarket thermoswitch are both black is because they can't really be mixed up. Finally, if I jumper the two wires I have connected from the harness to the thermoswitch on the harness side, the fan should come on if the rest is connected right. I just don't want to short anything out if they aren't right!

I know this diagram is easy, but the thing throwing me off is the fact that there is a yellow/white wire to a fan relay for an AC car. I say this because I just cut all of the ends off without labeling them, so I was thinking maybe I'm working with two yellow and whites because one shouldn't be there in my case. Wiring harnesses aren't specific, as I have connectors all over for AC and stuff like that aren't being used. The blue/red to blue/red and black to black are easy, it's the two yellow/whites out of the harness that are throwing me off because I don't see where connector F24 and F23 go to.

Thanks! 

Edited April 9 by subaru1988

[scoobydube]

My 86 Turbo has no wiring to the engine mounted radiator fan.  The other auxiliary fan that blocks air flowing through the radiator and blocks cooling air to the turbo area, has wiring.  But I took it completely out with no over heating problems whatsoever.  I even went back to a single core radiator and have no problems.  Take it out.

[subaru1988]

23 hours ago, scoobydube said:

My 86 Turbo has no wiring to the engine mounted radiator fan.  The other auxiliary fan that blocks air flowing through the radiator and blocks cooling air to the turbo area, has wiring.  But I took it completely out with no over heating problems whatsoever.  I even went back to a single core radiator and have no problems.  Take it out.

Interesting.. I have to say that after I replaced my radiator/water pump, my car runs right in the middle or a hair below depending on outside temps. If the weather was always 80 or below, I might not worry about it. That said, 90+ degrees out while stopped in traffic is possible where I'm at! My fan does work, and I just wanted a second set of eyes to give some input on my wiring hookups and the diagram. The diagram is OK for the LR and B wires, but the YW go to-- not so sure. Shoulda labeled them, but I was in a hurry. Thanks!

Edited Sunday at 04:28 PM by subaru1988

[azdave]

On 4/9/2025 at 3:49 PM, subaru1988 said:

I know this diagram is easy, but the thing throwing me off is the fact that there is a yellow/white wire to a fan relay for an AC car. I say this because I just cut all of the ends off without labeling them, so I was thinking maybe I'm working with two yellow and whites because one shouldn't be there in my case. Wiring harnesses aren't specific, as I have connectors all over for AC and stuff like that aren't being used. The blue/red to blue/red and black to black are easy, it's the two yellow/whites out of the harness that are throwing me off because I don't see where connector F24 and F23 go to.

Thanks! 

If you had air conditioning and turned it on, the A/C fan would then be fed 12 volts but the fan would not run unless that same coolant snap switch was closed. At that point, both fans would turn on and off together as needed. I'm confident the extra Y/W wire would have been used to provide the switched ground connection for the A/C fan you don't have.

My 87DL is different. It has a fan belt driving the radiator fan (with old style thermostatic fan clutch) and it is always on of course. The electric fan for my A/C has a coolant snap switch to provide a ground connection when needed. My wagon is pretty much my daily driver here in Phoenix and used all summer long. I see about 3/4 scale on the factory temp gauge (not known for accuracy) and I have never had an issue with running hot once I installed an aftermarket single row to replace the heavily clogged OEM metal radiator.

[subaru1988]

On 4/14/2025 at 6:48 AM, azdave said:

If you had air conditioning and turned it on, the A/C fan would then be fed 12 volts but the fan would not run unless that same coolant snap switch was closed. At that point, both fans would turn on and off together as needed. I'm confident the extra Y/W wire would have been used to provide the switched ground connection for the A/C fan you don't have.

My 87DL is different. It has a fan belt driving the radiator fan (with old style thermostatic fan clutch) and it is always on of course. The electric fan for my A/C has a coolant snap switch to provide a ground connection when needed. My wagon is pretty much my daily driver here in Phoenix and used all summer long. I see about 3/4 scale on the factory temp gauge (not known for accuracy) and I have never had an issue with running hot once I installed an aftermarket single row to replace the heavily clogged OEM metal radiator.

If my car had a clutch fan like yours, I wouldn't even worry about the electric fan. From what you say, it sounds like the difference between my car and an AC car is a relay for the AC fan, as the diagram does show. My thoughts were when I redid the connections and connected it all back together, put the same colored wires with each other and that should do it, ie. LR to LR, YW to YW, B to B. Four from the harness, four total from the fan and the switch, couldn't be that hard, right? LOL

Good to hear you're driving in Phoenix in summer no less with no real issues. I agree with you on the radiator. I put a new one in my Subaru, and man, what a difference. Mine was literally falling apart too. The cooling fins were disintegrating, but it was somewhat hidden by the rad fan. Made all the difference! I barely get over 1/2, usually under if it's cooler out, whereas before it was pegged at 3/4 all the time regardless of outside temps.\

My thought is the fan is there, it works, why not try to at least hook it up right. Too bad the factory connectors blistered up from heat thanks to being badly corroded. That could actually be why some people's fans don't work. I would have never known without smelling burning plastic!

Edited Tuesday at 05:26 PM by subaru1988

[azdave]

21 hours ago, subaru1988 said:

My thought is the fan is there, it works, why not try to at least hook it up right. Too bad the factory connectors blistered up from heat thanks to being badly corroded. That could actually be why some people's fans don't work. I would have never known without smelling burning plastic!

Yup. Corrosion creates high resistance connections that will heat up and ruin the compression/slip fit of the terminals and then it melts everything around it, all without ever blowing a fuse. I'm okay with the non-electric fan on my DL but it was tough finding a good thermostatic clutch when mine seized up last fall. I ended up finding one at PicknPull from a GL-10. It looked brand new and has been working great.